Those states each have more than 1 million tax-credit-eligible residents (Texas with 2 million people; California with 1.9 million people and Florida with 1.6 million people), and another seven states have more than 500,000 tax-credit-eligible residents, Kaiser found.

The states with the fewest number of residents to qualify are Vermont, with 27,000 individuals, and the District of Columbia, with 9,000.

Under PPACA, people with incomes between 100 percent and 400 percent of the federal poverty level may be eligible for premium tax credits when they purchase coverage in an exchange. The amount of tax credit that eligible people can receive depends on several factors, including their family income and the cost of insurance where they live.

Earlier, the Congressional Budget Office estimated that 7 million uninsured people would gain coverage through the exchanges, with 6 million qualifying for subsidies.

For their estimate, Kaiser used data from the 2012 and 2013 Current Population Survey Annual Social and Economic Supplement.